EP1102282 A1 discloses devices surrounded by an inner and an outer layer. The outer layer provides chemical resistance and abrasivity ([0011]) and the inner layer provides flame retardancy and high elongation and tensile strength ([0011]). One example of an inner layer is Rezeptur 7 in Table 1 of page 6. The layers are described as providing a high elongation. In order to provide a desired adhesiveness between the layers, the layers can comprise block copolymers. However, as shown in Example 2 herein, block copolymers do not provide the highest elongation at break. Furthermore, EP1102282 A1 does not teach the relevance of the type of polyolefines regarding the elongation properties.
Compositions comprising polyolefin elastomers (POE) in combination with a high density polyethylene (HDPE) and a polyethylene having a density of below 0.910 g/cm3 as well as a flame retardant, a coupling agent, and a stabilizer are known in the art. Using a combination of HDPE and VLDPE (very low density polyethylene) is known for achieving good elongation properties. However, the use of HDPE is neither required nor desirable in the context of the present invention.
Other known polymer compositions may provide an elongation of only up to about 300%. Such compositions may include an ultra-high molecular weight polysiloxane.
DE3633056 A1 teaches that VLDPEs increase the resistance to thermal distortion (claim 5). It neither discloses nor suggests using a combination of the particular VLDPE and particular polyolefin-elastomer of the present invention for providing a polymer composition having a high content of flame retardant filler.
WO 2010015876 A1, WO 2013030795 A1, and WO 2007032573 A1 disclose compositions which have an elongation at break below only 200%.
WO 2002026879 A1 discloses a halogen-free polymeric composition including: (a) at least two metallocene catalysed olefin polymers and/or copolymers wherein at least one of the olefin polymers and/or copolymers is elastomeric; and (b) an effective amount of at least one filler which is capable of providing the polymeric composition with flame retardant properties substantially similar to that of plasticised PVC (see claim 1). The composition includes at least about 30 PHR of at least one metallocene catalysed polyolefin elastomer (POE). For more flexible compositions, even higher POE contents are suggested. The present invention does not require such high POE contents in order to provide the desired elongation properties.
WO 2008014597 A1 and WO 2010024602 A2 disclose compositions having an elongation of up to about 800%. However, these compositions do not contain high levels of fillers which are flame retardants.
It is therefore an object of the present invention to provide elongated articles having good long term mechanical stability and flame retardancy, in particular low flammability, good resistance to pressure at high temperatures (mechanical protection), high elongation at break, good dimensional stability, high strength at break, and high flexibility. Other properties which may be good relate to the waviness (which is related to the intensity of the spiral appearance of a cable surface predefined by the twisted cores), stripping force for removal of the polymer composition from the elements, low friction, and resistance to scratches.